The present invention relates to implantable devices, and in particular, to implantable devices for radiation therapy.
Ionizing radiation is employed in the management of a wide variety of malignant tumors, providing a mechanism whereby the malignancy can be destroyed while the normal tissues are preserved. With preservation of normal tissues, normal function and normal appearance may also be preserved. Hence, ionizing radiation forms part of the treatment for over half of all patients with cancer. The overall effectiveness of radiation therapy, however, depends upon the balance between effective tumor control and morbidity due to the treatment. It is understood that the differential effects of ionizing radiation on tumors and normal tissues gives rise to a favorable therapeutic ratio for most patients. However, radiation can have destructive immediate and delayed effects on normal tissues. Techniques employed for radiation therapy significantly affect the incidence and severity of these destructive effects.
Because all types of ionizing radiation affect tissues via the same basic physical mechanisms, differences in spatial or temporal distributions are responsible for different effects observed with equal physical doses. The method for delivering radiation thus becomes highly significant. Treatment modalities for delivering therapeutic ionizing radiation include external beam radiation and direct placement of radioactive sources within tissues. This latter technique, termed brachytherapy, may permit delivery of ionizing radiation to a tumor in higher doses than those achievable with external beam radiation. Conventional external beam radiation treatments rely on multiple fractions of dose in order to ensure that the highest fractions of tumor cells are exposed at the most sensitive parts of the cell life cycle. Brachytherapy implants, such as brachytherapy seeds, on the other hand, can supply a continuous and highly localized radiation dose to the surrounding tissue. Because a delivered dose from a radiation source decreases proportionately to the square of the distance from that source, brachytherapy permits the delivery of very high radiation doses to those areas of a tumor in close proximity to the implant, with relative sparing of more distant tissues. With careful placement, so that the radiation source is in proximity to the tumor and distant from normal tissue, effective therapy against the tumor may be combined with minimal collateral damage to normal tissues. A variety of radioisotopes, including 125Iodine, 103Palladium, 137Cesium, and 192Iridium, may be used in the treatment of cancers involving such tissues as the breast, the prostate, the brain, along, the head and neck, the female reproductive tract, the musculoskeletal system and related soft tissues, and the eye.
As understood herein, those radioactive sealed sources employed in brachytherapy implants will be termed xe2x80x9cseeds.xe2x80x9d Commonly, seeds are intended for permanent implantation. A description of certain types of seeds can be found in B H Heintz et al., xe2x80x9cComparison of I-125 sources used for permanent interstitial implants,xe2x80x9d Medical Physics, Vol. 28, No. 4, p. 673 (April 2001), the contents of which are hereby incorporated by reference. Certain devices known in the prior art are intended for insertion directly into the tissues without employing a needle or other similar delivery device. An example of such a device may be found in the disclosure of U.S. Pat. No. 4,815,449. This patent provides, in certain embodiments, an implant of sufficient rigidity to be driven into a tumor without deflection, so that the implant may be used independently of a positioning or delivery device.
Alternatively, brachytherapy seeds may be positioned in the tissues to be treated by insertion through a delivery device, for instance, a needle. Using a delivery device may allow more precise positioning of seeds in areas requiring treatment. Brachytherapy seeds from various manufacturers may be made to the same set of specifications so that they are compatible with those delivery systems in common use. In those delivery systems, the seeds may be preloaded into needles or other delivery devices. The position of a plurality of seeds within the delivery device may be maintained by placing loose spacers between the seeds to establish and maintain a desired positioning. Once the seeds are positioned in the delivery device, insertion into the tissues takes place. To insert the seeds, the needle containing them must first be inserted to a preselected depth into the appropriate position in the patient""s tissues. An injection mechanism such as a mandrel may then be inserted into the needle with its distal end in contact with the seeds. The needle, thereafter, may be withdrawn over the mandrel, leaving the seeds and loose spacers resident in the preselected tissue area. Once positioned within the tissues using this method, the seeds and loose spacers are free to move from their original position, as there are no constraints on the position or orientation of the seeds. This can lead to the undesirable consequence that dose distribution within the tissue may be changed. For instance, movement of the seeds after deployment can change the area being irradiated, and can change the dose being delivered both to the preselected tumor regions and to the surrounding normal tissues.
There remains, therefore, a need for a system that can retain the brachytherapy seeds in position relative to one another prior to delivery, and which can retain the position of the brachytherapy seeds in relation to the tumor after the seeds are delivered into the tissues.
The present invention provides, in one embodiment, an implantable device for radiation therapy of pathological tissues. The device, in an embodiment, includes a substantially tubular member having opposing ends, a central section into which a radioactive sealed source is positioned between the ends, and a socket at each of the opposing ends. The device further includes a spacer partially positioned within one of the sockets, such that the blunt end on the spacer is exposed.
In another embodiment of the invention, an assembly of a plurality of tubular members, each having opposing ends, a central section into which a radioactive sealed source is positioned between the opposing end and a socket at each of the opposing ends. The assembly further includes a spacer positioned between two tubular members, such that the spacer is partially retained within one socket of each tubular member, to permit joining of the tubular members in series along a common axis.
In a further embodiment, the invention provides a method for manufacturing a brachytherapy implant. The method includes providing a tubular member having opposing ends, a central section positioned between the opposing ends, into which is placed a radioactive sealed source, thereby creating a socket at each of the opposing ends. Next, a spacer may be placed within a socket and subsequently secured therein. A second spacer may be placed in the opposing socket and subsequently secured therein.
A method of treating pathological tissues is also provided in accordance with an embodiment of the present invention. Initially, a site of pathological tissues is identified. Next, an implantable device is provided. The device, in one embodiment, includes at least one substantially tubular member having opposing ends, a central section into which a radioactive sealed source is positioned between the opposing ends, a socket at each of the opposing ends. The device, in another embodiment, includes at least one spacer positioned within one of the sockets of the device. The device can thereafter be placed within a lumen of a delivery mechanism. Once the implantable device is placed within the lumen, the delivery mechanism can be inserted at the site having the pathological tissues to a depth that permits access to the pathological tissues. Subsequently, the implantable device can be delivered from the lumen of the delivery mechanism to the site of the pathological tissues.
The device, in another embodiment, includes a spacer that is echogenic, enhancing the ultrasonic visibility of the spacer and, indirectly, enhancing the determination of the location of the attached radioactive sealed source.